Accounts due 30 September: what a dormant company with a 31 December year end must file

By Ben Davies · Updated 26 September 2026

More UK companies have a 31 December year end than any other date, which makes 30 September the busiest accounts deadline of the year at Companies House. For a dormant company (no money in or out of its books all year — Companies House calls these 'significant accounting transactions') the filing is short, but the deadline is exactly as hard as it is for a trading one.

What is due by 30 September

Annual accounts for the year to 31 December. For a genuinely dormant company that is a one-page balance sheet with the required statements — just share capital, or the figures a company that once traded still carries, unchanged from last year. For a non-trading company with a transaction or two — repaying a Bounce Back Loan, for example — it is a set of FRS 105 micro-entity accounts (the short accounts for a company that isn't trading but had some money move) instead.

That is the only thing due on 30 September. The confirmation statement runs on its own anniversary date, and the nil CT600 (a Company Tax Return showing no tax to pay) for the same year is due 12 months after the period end — 31 December — for the period HMRC has asked for.

What happens on 1 October

The penalty is automatic: £150 for private companies if the accounts arrive within the next month, rising to £375 after a month and £750 after three. Being dormant is not a defence and is not a ground for appeal. If the company was also late last year, the penalty is doubled.

Leave it long enough and Companies House will begin strike-off action, which puts the company's name and its bank account at risk.

First accounts are different

A company incorporated with a 31 December year end does not owe its first accounts on the following 30 September. First accounts cover the period from incorporation to the first accounting reference date and are due 21 months after incorporation. If you are unsure which applies, the deadline calculator reads the answer from Companies House.

Being done in minutes

On a DormantFile plan the accounts for the year to 31 December are prepared from the company's own record and filed to Companies House in about two minutes, with the nil CT600 handled in the same place when its own date comes round. If you only want the date watched, the free watchdog emails you 90, 30, 14, 7, 3 and 1 day before 30 September — no card needed.

Key points

• 31 December year end means accounts due 30 September (from the second year onward).
• Nothing else is due that day; the CT600 has its own 12-month deadline.
• The penalty starts at £150 on 1 October and doubles for a second late year.
• Weekends do not extend the deadline.